Change an Aircraft Oil Filter in 17 Easy Steps

Do you want to learn how to easily change your aircraft’s oil filter and save yourself the cost, and time, of having others do it for you?

This post will teach you how to service your own oil filter, whether it is a spin-on or a cartridge type of oil filter. We will specifically cover:

Different types of oil filters and which you should use

Which oil filter system is the easiest to install and maintain

Time-saving tips

Aircraft oil filter inspection

Required tools for the job

And other tips and tricks

Types of oil filters: Spin-on and Cartridge

When you begin to research and learn about aircraft oil filters, the first thing you will usually discover is there are two options, spin-on oil filters and cartridge oil filters. When differentiating between the two, it is common knowledge amongst mechanics and general aviation DIY types that the cartridge oil filter typically requires more work and more chance of leaks.

Both of these oil filters come in a short and a long version. Choosing between a short or long version will depend on the clearance area within your aircraft engine’s accessory case and firewall.

If you have the space, a long oil filter is preferable due to its greater filtration capacity and the time in between oil changes.

Full flow oil filters

These filter types are referred to as full flow oil filters because they are mounted downstream from the engine oil pump. When oil circulates it passes through the oil pump and the oil filter, there is no diversion of oil in this process like there is in the bypass oil filter system.

Within this system is a safety mechanism that allows oil to be diverted if the oil pressure becomes too high. This pressure-relief valve can be a literal life saver if you begin to experience oil problems.

Bypass oil filter system

The bypass oil filter system is not mounted downstream like the full flow oil filter system. It is mounted parallel to the oil pump. Only 10% of aircraft use this system.

The only time you would need to consider this system is if you have purchased a special oil filter that can restrict flow. This is not a preferable filter for a full flow system.

Replacing a cartridge oil filter

For quicker reading, the key steps are bolded.

To begin with, you must remove all of your safety wire. IMPORTANT: pay close attention to the location of the safety wires for reinstallation.

For the next step, you will want to consider using a form-a-funnel flexible draining tool or some type of bucket to catch oil drippings. Begin by using a 1-inch open-end wrench (or socket wrench) to unscrew the hollow stud at the top of your aircraft oil filter.

Next, turn the filter over and remove the filter-to-engine gasket. Discard this gasket and then unscrew the nut from the end of the stud. Once you’ve completed this, push the stud out of the oil filter.

Now that you have the oil filter deconstructed, take out the oil filter element and KEEP IT. Do not discard this. You will want to cut this open and examine it later.

Take out your stud and thoroughly clean it using gasoline, and then wipe it dry with a clean rag.

You will want to check your cartridge for any imperfections. Find a perfectly flat surface and place the cartridge upright on this surface. You should measure this cartridge for out-of-flat condition. Anything greater than 0.010 inches at the rim should be replaced. Also, look for any damage or imperfections on the can that could become an issue in the future.

Your next step will be to install a new copper washer, two new rubber gaskets and the ends of the oil filter. Make sure to lubricate all of these pieces with engine oil before replacing.

Now that you have the lubricating completed, install the new gasket on the outer surface of the lid. As you do these steps, always be looking for any deformities or damage to your aircraft parts.

After you’ve installed the new gasket, you will want to replace your filter assembly on the aircraft oil filter adapter. When doing this, pay attention to the placement of your safety-wire tabs. These should be on the proper side so you can rewire them.

Using your aircraft oil filter torque wrench, tighten the stud to the specified torque. If you do not know what torque it should be at, reference your aircraft service manual.

Next, you will want to put the proper amount and grade of engine oil back in your engine and start your engine. After it runs awhile check for any leaks, check the torque of your stud, and look to see if your oil filter adapter remained secure to the engine.

The last step you will want to complete is the replacement of the safety wire. If you aren’t aware how to properly do this, reference your aircraft’s service manual to see proper instructions.

Replacing a spin-on oil filter

Luckily, spin-on oil filters are much easier to replace than the cartridge oil filters!

Before you do anything, you will want to obtain the correct part number that coincides with your aircraft’s engine.

Begin by removing the safety wires and unscrewing your oil filter. As mentioned before, pay close attention to how the safety wires are installed. You will need to put them back in the correct positions later. Also don’t forget to have some kind of container underneath your oil filter to catch the excess oil that will spill out.

TIP: While performing these steps, take a look at the filter mount. Which way is it pointing? If it is pointed up or horizontally, be ready for it to release oil when you remove it.

When removing a spin-on oil filter, you’ll often find it has become stuck to the mounting pad. Luckily, todays filters have a 1-inch steel hex on top of the can where you can use an oil-filter torque wrench to free the filter.

After you have removed the filter, inspect it for any deformities or damage. Take a close look at the male end of the filter for any wear and tear.

Next, you’ll need to prelubricate the new filter with engine oil and screw the new filter until the gasket makes contact with the oil filter mounting adapter.

TIP: Make sure not to torque the filter more than 1-3/4 turns after you make contact with the mounting pad. If you do this, you may never get it back off again.

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